The major objective of the program is to study the natural history of perinatal cytomegalovirus (CMV) and group B Streptococcal infections in mothers, infants and children by large scale, prospective and longitudinal investigations. The CMV studies include in the mothers: 1) the role of recurrent versus primary infection in intrauterine and intrapartal transmission; 2) mechanisms of fetal transmission with recurrent maternal infection; and 3) effect of pregnancy hormones on growth of CMV. In infants and children they include studies on: 1) long term developmental outcome, 2) assessment of immunologic assays for detection of silent infection in the newborn, 3) pathogenetic studies of severe disease, and 4) nature of immune complex formation in congenital CMV. In addition, longitudinal studies of the humoral and cellular immune response in the maternal, congenital and natal infections are to be determined and related to virologic and clinical parameters over time and human strains are to be genetically analyzed and related to the disease state in man to search for microbial virulence factors. The group B Streptococcal studies include prospective and longitudinal epidemiologic studies of strain specific colonization of mothers and infants and the role of the bacteria in both infectious and non-infectious complications of pregnancy. Modes of transmission from mother to baby and hospital spread will be sought. Serologic assays for detection of antibody will be developed and along with current assays compared for utility in investigating pathogenesis. In sick infected infants, bacteriologic and immunologic studies will be performed to better understand the early and late onset forms of group B infections to better define the pathogenesis of the two disease states in hopes of developing better therapeutic or preventive approaches in the future. Both the CMW and streptococcal studies are to be integrated for correlative analyses in situations where deemed pertinent.